Using both balanced and unbalanced outputs

Glad I never read the article saying not to use both. My Pre-3 has the unbalanced outs feeding my sub while the balanced outputs feed my amps (bi-amping a pair of PS Audio A-100s). No problems yet.
I would expect a switch that would disable the non-used output if it was hazardous.

I own one and just checked the owner's manual. There is nothing in there about not using both XLR and RCA outputs at the same time. However, their other products (such as the DAC 3) emphatically state that using both outputs at the same time could damage the unit. I'd check with BelCanto directly to see what they say, but I think if it were problematic they'd have warned you already. LEt us know what you find out.